Projector systems are generally devices that integrate light sources, optics systems, and electronics for front- or rear-projection of images from computers or video devices onto walls or screens, for large-image viewing. They are especially popular among business users who give presentations as part of their job responsibilities. Newer projectors can weigh as little as a few pounds, making them well suited for business travelers. As the quality of projection technology has improved, projectors are also finding their way into peoples' homes for high-definition television (HDTV) and other home entertainment applications.
One type of projection system is a digital projection system that utilizes spatial light modulators (SLM's) to project image data therefrom. Examples of SLM's include liquid crystal display (LCD) SLM's, and digital micromirror device (DMD) SLM's, Liquid Crystal on Silicon (LCoS) SLM's, as well as other types of SLM's. There may be one pixel on each SLM in the projector for each pixel of digital image data to be projected. The projection system controls the SLM pixel or pixels in accordance with the pixel of the image data to which the SLM pixel corresponds. The SLM pixel modulates the light that is incident to the SLM pixel in accordance with the image data pixel, and the projector projects the pixel.
Light sources when combined with reflectors and or lenses typically found in digital projection systems output converging, diverging or collimated light that, due to the nature of the light sources, is more bright at the center of the beam than at the edges of the beam. If this light from the source and the reflector is used to illuminate the SLM it will be too bright in the center of the SLM and dimmer around the edges. Left uncorrected, such light results in image projection that may be too bright at the center of the image and too dim at the edges of the image. To correct this problem, digital projection systems typically include illumination systems with complicated optics mechanisms that are made up of a number of lenses, mirrors, and/or condenser optics. The purpose of the illumination system is to capture light from the source and spatially homogenize the light so that it can provide essentially uniform illumination of the SLM, so that this can be imaged onto the screen for viewing. Even then, however, the problem is not completely corrected, and including such sophisticated illumination optics mechanisms raises the costs of digital projectors.